#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>
int fib(int n) {
	int a = 1;
	int b = 1;
	int c = 0;
	if (n <= 2) {
		return 1;
	}
	while (n-2) {
		c = a + b;
		a = b;
		b = c;
		n--;
	}
	return c;
}
int main() {
	int n;
	scanf("%d", &n);
	int r = fib(n);
	printf("%d", r);
	return 0;
}